Splittable tow

ABSTRACT

A CRIMPED TOW COMPRISING A RIBBON OF CRIMPED PARALLEL CONTINUOUS FILAMENTS READILY SPLITTABLE BY PULLING OPPOSITE SIDES OF THE BAND.

May 11., 1971 J. N. GRAY ETAL 3,578,551

SPLITTABLE TOW 3 Sheets-Sheet 1 Filed April 18, 1969 M ny JACK N. GRAYGEORGE A. WATSON ATTORNEY y 11, 1971 J. N. GRAY AL 3,578,551

SPLITTABLE TOW Filed April 18, 1969 Z: Sheets-Sheet 2 TiciE.

INVENTOR JACK N. GRAY GEORGE A. WATSON BY M ( ATTORNEY May 11, 1971 YEITAL 3,578,551

SPLITTABLE TOW Filed April 18, 1969 3 Sheets-Sheet 5 INVENTOR JACK N.GRAY GEORGE A. WATSON ATTORNEY United States Patent 3,578,551SPLI'ITABLE TOW Jack N. Gray, Columbia, S.C., and George A. Watson,Davidson, N.C., assignors to Celanese Corporation and Fiber Industries,Inc., both of New York, N.Y. Original application July 13, 1964, Ser.No. 382,017, new Patent No. 3,439,394, dated Apr. 22, 1969. Divided andthis application Apr. 18, 1969, Ser. No. 817,508 Int. Cl. D02g 3/00 US.Cl. 161-173 5 Claims ABSTRACT OF THE DISCLOSURE A crimped tow comprisinga ribbon of crimped parallel continuous filaments readily splittable bypulling opposite sides of the band.

This invention is a divisional application of copending application Ser.No. 382,017, filed July 13, 1964, now Pat. No. 3,439,394.

Man-made fibers which are to be cut into staple fiber length are oftensupplied as tows which are bundles of generally parallel continuousfilaments, each such bundle containing a large number of such filaments,generally well over 500, e.g. 6,000 to 500,000. In one process for themanufacture of tows, suitable for use in making staple fibers, a numberof sub-tows, each containing only a fraction of the filaments desired inthe main tow, are first fed side-by-side to a draw frame where they arestretched, in a manner well known to the art (as discussed for examplein Man-Made Textile Encyclopedia, edited by J. J. Press, published 1959by Textile Book Publishers, Inc., pp. 75 and 76), to develop the desiredphysical properties (e.g. high tenacity and stiffness); the resultingdrawn tow is then fed to a crimping device, which is preferably of thestufling box type, where the filaments are crimped, and then, inuntensioned condition, onto a belt which transports the crimped towcontinuously through an oven maintained at a temperature sufiicientlyhigh to set the crimp permanently, but not high enough to damage or meltthe filaments.

The draw frame, crimping device and oven are utilized most eflicientlywhen the tow passing therethrough contains a very large number offilaments, e.g. tow whose total denier is over 200,000 and whichcontains over 40,- 000 filaments. However, for certain uses the crimpedheatset tow must be considerably lower in weight or in filament count.For example, certain commercial tow-to-top or two-to-yarn convertingmachines, which are standard equipment in the mills of yarn spinners whopurchase tow, are not equipped to handle heavy tows of higher totaldenier than 200,000.

It is an object of this invention to provide a heavy tow which may beused as such and which may also be split easily, without materialdamage, into a plurality of smaller tows which may be processed readilyon presently available tow-to-top converting machines.

Another object of this invention is the provision of a novel process forthe production of splittable tow.

Still another object of this invention is the development of a methodfor making a plurality of relatively light crimped heat-set tows whileprocessing a tow of heavier weight through a draw frame and crimper.

Other objects of this invention will be apparent from the followingdetailed description and claims. In this decription and claims allproportions are by weight unless otherwise indicated.

In accordance with one aspect of this invention, a splittable tow isproduced by passing to a crimping zone two parallel tow bands, each madeup of continuous parallel untwisted filaments in which the cohesionbetween the filaments within each band is greater than the cohesionbetween the bands. The tow leaving the crimper has the same generalappearance as the tow made by feeding to the crimping zone a singlelarge band, instead of the plurality of smaller bands, and it may behandled in the same manner in the setting oven. Thus it may be laiddown, as a single cohesive tow, in a sinuous path backand-forth across amoving belt passing to said oven and may be there treated to set thecrimp. It is found, surprisingly, that the tow may be easily split byhand merely by grasping one side of the tow and pulling it gently whilerestraining the other side. The splitting takes place without anysubstantial breaking or tearing of the filaments of the tow, to producetwo cohesive smaller crimped tows corresponding to the tow bands fed tothe crimping zone; of course, if more than two bands are fed to thecrimping zone, the tow will be splittable into a correspondingadditional number of smaller tows.

In the drawings, which illustrate one embodiment of the invention,particularly suitable for the making of polyester tows:

FIG. 1 is a diagrammatic view, in elevation, of the process for theproduction of splittable tow,

FIG. 2 is a plan view (partly broken away) showing the tow in the drawzone,

FIG. 3 is a diagrammatic view in elevation, of a modification in whichthe tow is split before packaging,

FIG. 4 is a diagrammatic view, in elevation, of a modification in whicha divider adjacent the crimping zone is employed,

FIG. 5 is a view, also in elevation, taken at right angles to FIG. 4,and

FIG. 6 is a photograph of the splittable tow shown during the splittingthereof.

Turning now to FIG. 1, reference numeral 1 designates subtows ofcontinuous filaments, each subtow, for example, containing in the rangeof about 500 to 10,000 filaments and having a total denier in the rangeof about 750 to 150,000. The subtows, which may be supplied as coils insuitable containers, are taken through a guideboard 2, having aperturesthrough each of which a subtow passes, and then in parallel,closely-spaced paths over and under a set of spaced, fixed, straight,round tensioning bars 3.

During the beginning of their passage around the tension bars 3 thesubtows dip into a bath 4 of aqueous finish containing in lowconcentration (e.g. 1%) a textile finishing agent, such as a lubricantor antistatic agent. The material then passes over a set of driven feedrolls 6 through a drawing zone 7 to a set of draw rolls 8, 8a and 8b,each of which is driven at a peripheral speed substantially greater thanthe peripheral speed of the feed rolls, so as to stretch the. filamentsappreciably (e.g. with a draw ratio in the range of about 2.5 :1 to-6:1). The peripheral speed of the second draw roll 8a is slightlygreater than that of the first draw roll 8, and the peripheral speed ofthe third draw roll 8b is similarly greater than that of the second;this may be effected by making the rolls of successively greaterdiameters: and driving them at equal rotational speeds; the peripheralspeeds of the feed rolls are similarly increased along the path of thetow. From the last draw roll the tow passes through a dancer rollarrangement 9 and then over a guide 11 to the nip between the inletrolls 12 of a stutfer crimper 13.

The holes in the guideboard 2 are so arranged that the subtows aredelivered to the tension bars 3 in two sets (with the subtows in eachset being very close together and the two sets being spaced somewhatfurther apart). *For example, the subtows in each set may be spaced 0.5inch on centers with the outermost filaments of one subtow on theinitial tension bar 3a being only 0.1

inch from the outermost filaments of the adjacent subtow of the sameset, while the outermost filaments of the adjacent sets are spaced about1 inch apart. As the subto-ws pass over the tension bar 3 and feed rolls6, the filaments move laterally somewhat, since the tension on thesubtows engenders forces normal to the surfaces of the tension bars andfeed rolls, which forces tend to flatten the subtows against theseelements and thereby widen said subtows causing the outermost filamentsof adjacent subtows within each set to overlap. Intermingling of thefilaments takes place in the draw zone by reason of the interaction ofeach tow band with the corresponding sloping shoulder 16 or 17 of aconverging device 18 situated near the outlet of the draw zone andconsisting of a double frusto-conical freely rotatable roller mountedwith its crotch 19 slightly below the straight line draw path betweenthe bottom of the last feed roll 6b and the bottom of the first drawroll 8 and with its conical shoulders 16 and 17 (which may make anangle, for example, of 60 with the axis of the roller and thus an angleof 60 with each other) extending into that straight line path so thatthe tow bands 21 and 22 each engage one of said shoulders. It will beevident that because of the tension on the bands 21 and 22 theirfilaments will tend to migrate along the shoulders 16 and 17,respectively, towards the straight line draw path, referred to above;this will cause intermingling of the filaments of each tow band.

The tow bands which are, for example, about inch apart as they leave theconverging device 18 tend to flatten out against the surfaces of thedraw rolls 8, 8a and 8b under the influence of the forces, normal tosaid surfaces and engendered by the tension on the tow, so that the towleaving the draw rolls and fed to the crimper has the appearance of asingle band (although close inspection of the center portion of the bandwill reveal a line where there is little, if any, crossing over offilaments).

The tow entering the stufi'er crimper 13 is still moist, having amoisture content in the range of about 20 to 50%, for example. Thestuffer crimper 13 may be of conventional type having a pair of feedrolls 12 leading to a rectangular main body 26 whose width is about thesame as that of the tow fed to the crimper feed rolls 12 usually in therange of about 1 to 2 inches, e.g. about 1 /2 inches) and whose depth,perpendicular to said width, is about 1% inches at the top and less atthe bottom, the body being tapered downwardly. The outlet of the mainbody 26 is resiliently closed off by a suitably biased flapper 27, as iswell known in the art.

The single band of tow leaving the stutter crimper has numerous crimpsin approximate registry across the width of the band; generally it has afine crimp, for example, in the range of about 4 to 20, e.g. to 16,crimps per inch superimposed on a coarse crimp, of much largeramplitude; thus there may be about 2 to 5 coarse crimps per inch. Thetow band (still containing about 5 to 15% moisture at this stage) ispassed through a distributor 28, which may be of the usual typecomprising a pivoted tube, generally of sufficient width to accommodatesaid band without folding, which is swung back and forth about its pivot29 by any suitable mechanism to deposit the tow in a sinuous path acrossthe width of a driven endless belt 31 which carries the tow, restingthereon in substantially tensionless condition, through an oven 32 whichis desirably maintained at a temperature sufiiciently high to set thecrimp in the filaments of the tow (e.g. a temperature in the range ofabout 85 to 180 (1.).

The tow leaving the oven 32 may be drawn off the belt 31, cooled to roomtemperature, and laid into a carton 33 in the usual manner, as by meansof a distributor 34 which traverses the tow back and forth and side toside, followed by pressing of the thus formed bale in the carton, e.g.to a density in the range of about to 30 lbs. per cu. ft. e.g. about 20lbs. per cu. ft.

Alternatively the tow leaving the oven may simultaneously split into twobands and drawn off the belt 31, as shown in FIG. 3, with each bandgoing to its own carton, Where it is baled as described above.

The splittable tow of this invention preferably has the same overallappearances as the known non-splittable tows and may be handled, e.g.,coiled, baled, etc., as a unitary tow in the same way that such knowntows are handled. It is composed of generally parallel crimpedfilaments, with such filaments crossing and intermingling on each sideof the splittable line. If the tow is not treated to deregister thecrimps, the crimps (particularly the coarse crimps, previouslymentioned) will be in registry giving the appearance of waves extendingfor substantial portions of the width of the tow, with most of thewaves, or at least a large fraction thereof, extending across thesplittable line so that the line is not readily distinguishable (seeFIG. 6). One convenient technique for locating that line is by snappinga segment of the tow, as by holding the tow manually, with the handsspaced apart along its length, bringing the hands close together toallow the segment of tow to hang loosely between them, and then movingthe hands, still gripping the tow, sharply apart to place the segment oftow under tension; when this is done, the tow opens up along thesplittable line and the resulting split may be readily propagated,without any tearing or snarling of filaments, by simply pulling one-halfof the tow from the other, as FIG. 6.

In one specific example of the process described above, there were used14 undrawn subtows, each of 71,000 total denier and each containing2,130 filaments. The two bands on the last feed roll were each 2.5inches wide and were each narrowed to a Width of inch on the covergingdevice. In the drawing operation the tow was drawn through a draw zonewhich was heated with steam at atmospheric pressure using a draw ratioof 4.6:1 so that the total denier of the band leaving the last draw roll8b was 215,000. At this point, the band was 1% inches Wide. The entranceto the main body 26 of the stuffer crimper was 1 /2 inches wide. In thestuifer crimper the tow was subjected also to direct contact with steamsupplied in saturated condition at 20 p.s.i.g.

The tow leaving the outlet of the stuifer crimper was 1 /2 inches wideand had 12 fine crimps per inch, the amplitude of the fine crimps beingabout 0.06 (measured from peak to valley for single yarns) and 3 coarsecrimps per inch. The moisture content of the tow entering the crimperwas 30%; on leaving he crimper it was 10%. After heat setting for 20minutes at a temperature of about C. in the oven 32, the resultingsplittable tow was baled and compressed in the usual manner to a densityof about 20 lbs. cu. it. On unbailing, after the splittable line waslocated and the split started by snapping the tow, the tow could besplit easily into two identical non-splittable tows. The tow had atenacity of about 4.5 grams per denier.

FIGS. 4 and 5 show another arrangement within the broad scope of theinvention but generally less desirable because it usually involves sometearing of filaments and thus may produce a splittable tow leaving somebroken filaments along the splittable line. In this embodiment a singletow band with its filaments intermingled is fed from the draw zone tothe crimper feed rolls 12. Just before the entrance to the nip of saidfeed rolls, there is mounted a divider which may suitably be a bar 36having a rounded leading surface engaging the middle of the oncoming towband. The divider need not be large; thus good results have beenobtained with a divider 0.05 inch wide (measured in the plane of the towband perpendicular to the direction of movement of the tow). Theresulting two smaller bands formed by the presence of the divider arebrought together at, or shortly past, the crimper feed rolls 12 and, asin the preferred arrangement, the tow leaves the crimper as a singlecrimped band. In this embodiment it is preferred that any interminglingof filaments along the line to be contacted by the divider 36 belimited, since if there is considerable intermingling along this line inthe tow approaching the divider there will be considerable breakage offilaments at the divider, and also the force needed to pull the tow pastthe divider will be high, particularly when the tow is made of filamentsof relatively high tenacity (e.g. above 2 grams per denier).

As previously mentioned, more than two bands may be fed to the crimpingzone. This may be effected, for example, by the replacement of theconverging device 18 by a similar device having additionalfrusto-conical sections along its length or by the use of additionalbars 36. This, of course, results in a crimped splittable tow in whichthere are more than two non-splittable portions (i.e. more than twobands running lengthwise of the tow in which the filaments are somewhatintermingled). Advantageously, at least one of these non-splittablebands, and preferably all of them, have a total denier of at least50,000 and contain at least 10,000 continuous filaments. Thus thesplittable tow may, for example, include several such bands, separatedby splittable lines as previously described, with each such band havinga total denier of about 25,000 to 1,000,000 and containing about 300 to200,000 filaments, and made up of about 2 to 40 subtows.

The invention has been described particularly with respect to tows whosefilaments are of polyethylene terephthalate. It will be understood thatit is within the broad scope of the invention to carry it out with othertows, such as those made of other polyesters (e. g. the polyesters ofthe terephthalic acid and other glycols such as dimethylol cyclohexane),polyamides (such as nylon 6 or nylon 6,6), polyacrylonitrile andcopolymers thereof, polyolefines such as isotactic polypropylene, etc.These polymers may, if desired, be of the more easily dyeable typecontaining groups, e.g. SO Na or NH groups, which promote dyeability.

The splittable tows may be split to form two tow bands, each of whichmay be passed through a separate patterned roll arrangement (shown inCanadian Pat. 674,101, for example) and then through spreaders to formlightweight webs suitable for manufacture of battings and otherproducts. v

It is to be understood that the foregoing detailed description is givenmerely by way of illustration, and that variations may be made thereinwithout departing from the spirit of this invention.

The embodiments of the invention in which an exclusive propertyprivilege is claimed are defined as follows:

1. A crimped tow comprising a plurality of sub-tows in the form of acoherent ribbon of crimped, generally parallel, continuous filaments,with said continuous filaments crossing and intermingling on each sideof at least one splittable line, said crimped toW being readilysplittable to a plurality of corresponding tub-tows without anysubstantial broken or torn filaments by pulling opposite sides of saidcrimped tow, the portions of the tow of each side of said one or moresplittable lines being not so splittable owing to intermingling andcrossing over of the generally parallel filaments within said portions.

2. The product of claim 1 wherein two sub-tows make up said coherentribbon of crimped, parallel continuous filaments.

3. The product of claim 1 wherein said filaments are polyestercontinuous filaments.

4. A crimped tow as set forth in claim 1, and having crimps in registrywith ridges and troughs of registered crimps, extending across saidline, said tow being so cohesive that it may be folded, baled andunbaled without splitting along said line.

5. A crimped tow as set forth in claim 1, in Which said filaments are ofa glycol terephthalate polyester and have 4 to 20 crimps per inch, atleast one of said non-splittable portions having a total denier of about25,000 to 1,000,000 and containing about 300 to 200,00 filaments.

References Cited UNITED STATES PATENTS 3,235,442 2/1966 Stump 161-1733,277,537 10/1966 Roeder et al 19-66-T 3,384,932 5/1968 Watson 19-66TWILLIAM A. POWELL, Primary Examiner U.S. Cl. X.R.

